The following is more information on Japanese Maple Scale from the University of Maryland. This pest is on the increase in the region.
Japanese Maple Scale
We are finding 2nd generation crawlers of the Japanese maple scale active this week. The crawlers are purple and if you flip over the female covers you will see the purple colored females and the purple eggs she lays (as hown in photo). If you plan to make an application of Distance or Talus now it is the time to do it.
We are conducting trials at two Maryland nurseries for control of Japanese maple scale. Back in June these nurseries applied the insect growth regulator Talus and horticultural oil at the 1% rate for control of Japanese maple scale crawlers and early instars. The material worked well in killing newly settled crawlers and 2nd instars for about 3 weeks. The interesting thing is that the first generation females continued to lay eggs past this 3 week period. What we are seeing at the sites where Talus was used is that the 2nd generation crawlers are not present yet. We suspect that since we wiped out the early developing scale this took out the population that is producing crawlers at other locations. We plan to delay the next application at these two sites until crawlers start to show up.
Reprinted in part from the August 28, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from University of Maryland Cooperative Extension